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PRACTICAL ORGANIC CHEMISTRY

than rubber stoppers (which are attacked by many organic
liquids), and soften them well before use. The reactions
described at the end of each preparation are to be done in test-
tubes, and should not be neglected.
Above all, work with suitable, compact and clean apparatus
on a clean bench. The best results are usually obtained when the
preparation is carried out with something of the care and
accuracy of a quantitative analysis.
Where the asterisk occurs, it signifies that the operation must
be conducted in the fume cupboard.
Whilst the preparation is in progress, utilise the spare minutes
in reading the notes in the Appendix.
To facilitate reference to general manipulative processes,
which are described as they occur in conjunction with different
preparations, the following table is added.
Solids.                                       Page.
Filtration       ...............    53
Filtration under reduced pressure ...        ...    43
Crystallisation          ...        ...        ...        ...    52
Fractional crystallisation•   ......        ...   122
Sublimation  ...        ...        ...        ...        ...  226
Determination of melting-point    ...        ...    72
Liquids.
Dehydration...         ............    56
Determination of boiling-point      ...      ....    58
Distillation under reduced pressure          ...    84
Distillation in steam            ...        ...        ...   107
Fractional distillation    "     ...        ...        ...   136
Determination of specific gravity......    56
Liquids and Solids.
Heating under pressure......        24, 78
Determination of rotatory power......116
Mechanical stirring.........       90, 147
Purification of Methylated Spirit and Spirits of Wine
Methylated spirit, or spirits of wine 60—70 " over-proof, " may
generally replace the more costly absolute alcohol as a solvent
after undergoing a process of purification. The methylated
spirit must be of the old kind, consisting of a mixture of 9 parts
spirit of wine and i part purified wood-spirit, without the